A battery module has been mounted on an electric vehicle or the like from the related art. For example, the battery module is disclosed in Japanese Patent No. 5405102 and JP-A-2012-256466 which includes a cell stack body formed by a plurality of cells stacked in a front-rear direction and having a front surface, a rear surface, a left surface, a right surface, an upper surface, and a lower surface, a pair of end plates disposed on the front surface and the rear surface of the cell stack body, and a fastening frame for connecting the pair of end plates.
In this type of battery module, a load in a cell stacking direction of the battery module (hereinafter, appropriately referred to as a cell thickness constraint reaction force) occurs due to expansion of the cell caused by temperature change and aging deterioration. In recent years, since more active material is packed in the cell along with the high capacity and the high energy density of the cell, the cell thickness constraint reaction force tends to increase.
The battery module disclosed in Japanese Patent No. 5405102 includes side frames (metal bands) disposed on the right surface and the left surface of the cell stack body, and the side frames respectively include side frame bodies and a front flange portion and a rear flange portion that turn around the front surface and the rear surface of the cell stack body (the end plate) from the side frame body. In such a structure, since a load in a cell stacking direction due to expansion of the cell intensively acts on the front flange portion and the rear flange portion of the side frame, the large generation of bending stress may occur in a connection portion between front flange portion and the side frame body and in a connection portion between the rear flange portion and the side frame body.
In addition, the battery module disclosed in JP-A-2012-256466, is provided with side frames disposed on the right surface and the left surface of the cell stack body, and the front end and a rear end of the side frame are integrally fastened to the left surface and the right surface of the end plate via bolts. In such a structure, since a load in a cell stacking direction due to expansion of the cell intensively acts on the fastening portion of the side frame and the end plate, there may be a problem in that the bolt fastening portion is slipped or transformed.